Fuel storage tanks are often buried underground for reasons of safety. These underground tanks are filled from the surface through a fill pipe. The upper end of the fill pipe is often housed within a covered enclosure. This protects the fill pipe upper end from damage while providing easy access to the upper end when it is desired to refill the underground tank. Fill nozzles used to fill the underground tanks typically have automatic shutoff valves similar to those used at retail gasoline stations. On occasion the automatic shutoff valves either do not work quickly enough or do not work at all so that fuel overspills the upper end of the fill pipe. To prevent contamination of the surrounding area, overfill protection systems have been developed for these underground tanks. Typically an overfill catch basin is mounted around the fill pipe between the upper and lower ends of the fill pipe to catch the overspill. The overspill can then be pumped back into the main tank (see U.S. Pat. No. 4,655,361 to Clover, et al.) or drained back into the tank (see U.S. Pat. No. 4,637,522 to Klop).